9io Appendix II. Locomotive draught is induced up to 10" of water-head, and forced up to 2" by the current entering the front of ashpan. P. 698. Mechanical Stoking.—It is well known that hand firing is responsible for a large quantity of imperfectly-burned fuel, as well* as the emission of much smoke, and some form of machine stoking is therefore desirable, whose expected advantages- would be (i) smoke-prevention by uniform firing and constantly closed doors, (2) economy of fuel by using cheap coal and obtaining more perfect combustion, (3) economy of labour, (4) higher, more uniform, and more easily regulated evaporation. There are two forms of these machines : coking stokefs, where the coal is first fed to a dead-plate or its equivalent, for preliminary distillation ; and sprinklers, where the fine coal enters at the centre of the bars and is distributed by fans or beaters. We have only space for an example of the first, Fig. 873, as made by the New Conveyor Company. The hoppers A A contain small coal, placed there by mechanical elevators. This coal is fed slowly forward by the screw B, then coked at c, and pushed forward gradually by the movement of the firebars, which are connected to the crank shaft ix Finally the fuel arrives at E completely burnt, and simply drops down as ash.